Spring, mainspring, hairspring, and driving mechanism and timepiece based thereon

ABSTRACT

A mainspring used as a power source for a driving mechanism is made of an amorphous metal sheet, and has an S-shaped free-exploded shape. The curvature changing point, where the curving direction of the free-exploded shape changes is formed on the inner end side of a middle point between the inner end on the winding side and the outer end serving as the other end of the inner end. Because of the high tensile stress and a low Young&#39;s modulus, the amorphous metal permits increase in mechanical energy stored in the mainspring.

CROSS REFERENCE INFORMATION

This application is a division of U.S. application Ser. No. 09/297,289,filed Apr. 28, 1999, and currently pending.

TECHNICAL FIELD

The present invention relates to a spring used in a precision machinesuch as a timepiece, applicable, for example, as wielding means forfixing a crystal oscillator composing a timepiece or the like, or as apower source for a driving mechanism of a timepiece, a music box or thelike.

BACKGROUND ART

Various springs have conventionally been adopted in precision machinessuch as a timepiece and a music box. In a timepiece, for example, thereare known a spring fixing a crystal oscillator of a crystal oscillatingtimepiece in a wielded state, a mainspring composing a power source fora driving mechanism of a timepiece, a click spring provided forpreventing back-winding upon winding a mainspring, and a hairspringwielding a timed annular balance in a mechanical timepiece.

Conventional materials applicable for these springs include springmaterials and mainspring materials such as carbon steel, stainlesssteel, a cobalt alloy, and a copper alloy. These materials have howeverthe following problems.

1. The spring fixing a crystal oscillator in a wielded state poses aproblem in that the wielding force of the spring causes a shift in thepace of the crystal oscillator. More specifically, dispersion of thespring wielding force causes a gain or a loss of the period of a 32 kHzsignal issued by the crystal, and this leads to a problem of a shift ofaccuracy of a timepiece using this signal as a reference signal. Thesmallest possible dispersion of wielding force is therefore required fora spring fixing the crystal oscillator.

2. In a hairspring wielding a timed annular balance forming a governorfor a mechanical timepiece, a temperature change results in a change inYoung's modulus which in turn causes dispersion of the wielding force,and hence a change in the oscillating period of the timed annularbalance. This change in the oscillating period of the timed annularbalance exerts an important effect on the accuracy of a mechanicaltimepiece. It is therefore desirable to adopt a hairspring material, ofwhich Young's modulus does not change under the effect of a change intemperature.

3. Further, in the case of a mainspring serving as a power source for adriving mechanism of a timepiece or the like, a mainspring satisfyingcontradictory requirements of a long-time operation of the drivingmechanism and downsizing of the driving mechanism is demanded. Morespecifically, for example, a driving mechanism of a timepiece comprisesa mainspring serving as a power source, a barrel drum housing themainspring, and a train wheel transmitting a mechanical energy of themainspring by engaging with the barrel drum. Hands of the timepiece arerotated, via a transmitting unit such as the train wheel, by the use ofthe rotation force produced by the release of the tightly woundmainspring.

The number of turns of the mainspring serving as a power source of sucha driving mechanism and the output torque are in a proportionalrelationship. When the output torque of the mainspring is T, the numberof winding runs (number of turns) of the mainspring is N, Young'smodulus is E, the total length of the mainspring is L, and themainspring is assumed to have a rectangular cross-section having athickness t and a width b, it is known that T can be expressed by:T=(Et ³ bπ/6L)×N  (1)

On the other hand, the total length L, the thickness t and the width bof the mainspring are dependent on the size of the barrel drum housingthe mainspring. If the barrel drum has an inside radius R and a barrelarbor radius r, the total length L of the mainspring is determinablefrom the following formula:L=π(R ² −r ²)/2t  (2)It is thus suggested that the total length L and the thickness t of themainspring are in a inversely proportional relationship.

The mechanical energy accumulated in the mainspring is obtained byintegrating the output torque of Equation (1) by the number of turns N,and Equation (1) is considered to be a function of the total length Land the thickness t of the mainspring. The spring energy has thereforeconventionally been adjusted by controlling L and t.

This means that the maximum number of turns Nmax of the mainspring canbe increased by reducing the mainspring thickness t and increasing themainspring total length L.

On the contrary, the value of output torque T can be increased byreducing the total length L of the mainspring, and increasing themainspring thickness t.

As is evident from Equation (2), however, in this manner ofdetermination, the mainspring thickness t and the total length L arelimited by the volume of the housing space within the barrel drum. Whenadopting a mainspring operable for a long period of time, therefore, itis necessary to use a larger-sized barrel drum and a larger housingspace, thus leading to a problem of impossibility to downsize thedriving mechanism including the mainspring.

It was once conceived to achieve a mainspring capable of outputting ahigh torque with a thinner thickness t by adopting a mainspring materialhaving a high Young's modulus. This contrivance was however limited interms of mainspring durability since it was difficult to maintaintoughness of the mainspring.

The present invention has an object to provide a spring which permitsachievement of a high accuracy and stable operation of a precisionmachine such as a timepiece, and to provide a spring enabling, when usedas power source, to operate for a long period of time, and a drivingmechanism having this spring as a power source.

DISCLOSURE OF INVENTION

1. Specification of Spring Material

The spring of the present invention comprises an amorphous metal.

An amorphous metal is adopted as a spring material with a view toselecting a spring material having a large tensile stress and a smallYoung's modulus. More specifically, comparison of a conventionalmainspring material (chemical composition (wt. %): from 30 to 45% Co,from 10 to 20% Ni, 8 to 15% Cr, under 0.03% C, from 3 to 5% W, from 3 to12% Mo, from 0.1 to 2% Ti, from 0.1 to 2% Mn, from 0.1 to 2% Si, and thebalance Fe) and a spring comprising an amorphous metal reveals thefollowing result:

σmax (kgf/mm²) E (kgf/mm²) Conventional material 200 20,000 Amorphousspring 340 9,000-12,000

Applicable amorphous metals for the foregoing amorphous spring include,for example, Ni—Si—B, Ni—Si—Cr, Ni—B—Cr, and Co—Fe—Cr amorphous metals.Any of various amorphous metals can be adopted in response to therequired performance of the spring.

When adopting a spring comprising an amorphous metal as described above,a higher allowable stress is available because of a higher maximumtensile stress of the amorphous spring, and as compared with a spring ofthe conventional material having the same shape, a higher wielding forceis obtained: it is therefore suitable for downsizing a precisionmachine.

Since the spring comprises an amorphous metal, a wire or a ribbon caneasily be manufactured by any of the single roll process, the dual rollprocess and the rotation underwater spinning process, thus permittingsimplification of the spring manufacturing process.

Further, because of a satisfactory corrosion resistance of the amorphousmetal, it is possible to eliminate the necessity of rust preventiveplating for some portions.

When the spring comprising an amorphous metal is used as wielding meansfor fixing a crystal oscillator, it is possible to prevent a gain or aloss of the signal period of the crystal oscillator for the followingreason. As described above, the spring comprising an amorphous metal hasa low Young's modulus. As a result, the relationship between the amountof flexure ε of the spring and the wielding force F is as shown in FIG.1: it takes the form of graph G2 having a smaller inclination than graphGI representing a conventional material of spring. Therefore, when thespring of the conventional material giving a wielding force F0 necessaryfor fixing the crystal oscillator has an amount of flexure ε1, and theamorphous spring has an amount of flexure ε2, and if a change δ occursin the amounts of flexure ε1 and ε2 of the both springs, comparison ofchanges df1 and df2 in the wielding force F0 reveals that the change df2in the wielding force of the amorphous spring is smaller. By adoptingthe amorphous spring as wielding means for fixing the crystaloscillator, therefore, it is possible to reduce dispersion of thewielding force, minimize the shift of the period of the crystaloscillator, and thus improve accuracy of the timepiece.

If a spring comprising an amorphous material is adopted as a hairspringfor wielding a time annular balance forming a governor for a mechanicaltimepiece, a change in Young's modulus caused by a temperature change issmaller as compared with a usual hairspring material such as carbonsteel. Upon occurrence of a change in temperature, a change inoscillating period resulting from dispersion of wielding force isslight, thus permitting improvement of a mechanical timepiece.

Further, when adopting a spring comprising an amorphous metal as a powersource for a driving mechanism, i.e., in the case of a mainspringcomprising an amorphous metal, achievement of long-time operation of thepower source can be determined on the basis of the following concept.

More specifically, the flexure of a mainspring 31 (having a thickness t,a width b and a length L) can be approximately determined, as shown inFIG. 2, as a flexure of a cantilever supporting beam, of which the innerend 311 is rigidly connected to the barrel arbor 33, and the other outerend is left free. The flexure angle α (rad) in FIG. 2 can be expressed,when the mainspring 31 has a flexure radius r, by:r=L/α  (3)

The number of turns of the mainspring can be expressed, on the otherhand, by means of the above-mentioned flexure angle α as follows:N=α/2π  (4)

The above-mentioned equation (1) can therefore be transformed, fromequations (3) and (4), into:T=(bt ³ E/12L)×α  (5)

An energy U accumulated by the flexure of the mainspring 31 can becalculated by integrating a bending moment acting on the mainspring 31,i.e., an output torque of the mainspring 31 as to α:U=∫Tdα=∫(bt ³ E/12L)×αdα=(bt ³ E/24L)×α²  (6)

Consequently, the maximum energy Umax capable of being stored in amainspring having a length L can be expressed, if the maximum flexureangle of the mainspring 31 is canax, as follows:Umax=(bt ³ E/24L)×αmax²  (7)

The bending stress σ acting on the mainspring 31 is expressed as afunction of the bending moment acting on the mainspring 31, i.e., theoutput torque T that the mainspring 31 in a flexure state can output.When the displacement in the thickness direction from the neutral axis Aof the mainspring 31 is y, and the geometrical moment of inertia of themainspring 31 is Iz, then the bending stress a is expressed as:σ=T×y/Iz  (8)Therefore, the maximum bending stress σb in the tensile direction actingon the upper surface of the mainspring 31 in FIG. 2 calculated, fromequation (8):σb=T(t/2)Iz  (9)

The cross-sectional area of the mainspring 31, forming a rectangularshape with a thickness t and a width b, calculated as follows:

 Iz=bt ³/12  (10)

and from equations (9) and (10), this is expressed as:T=(bt ²/6)×σb  (11)

Consequently, T is expressed, from equations (1) and (11), as follows:T=(Et ³ bπ/6L)×N=(bt ²/6)×σb  (12)

The maximum number of turns Nmax giving α max in equation (7) is, fromequation (4):N max=αmax/2n  (13)

Therefore, the following relationship can be derived:αmax=2Lσb/Et  (14)

It is therefore suggested that αmax is determined by the maximum bendingstress σb in the tensile direction of the mainspring 31, i.e., themaximum tensile stress σmax of the mainspring material used for themainspring 31, and the above-mentioned equation (7) is calculated asfollows:Umax=(bt ³ E/24L)×(2Lσmax/Et)²=(btL/6)×(σmax² /E)  (15)

Equation (15) reveals that the maximum energy Umax stored in themainspring 31 in FIG. 2 varies not only with the thickness t, the widthb and the length L of the mainspring 31, but also with the maximumtensile stress σmax and Young's modulus E of the material forming themainspring 31.

In order to increase the energy Umax stored in the mainspring,therefore, it is desirable to adopt, for the mainspring 31, a materialhaving a high maximum tensile stress σmax and a low Young's modulus. Inother words, when adopting the foregoing amorphous spring havingσmax=340 (kgf/mm²) and E=9,000 to 12,000 (kgf/mm²) as a material for themainspring 31, it is known from equation (15) that an amount of energy4.8 to 6.4 times as large as that available in the conventional art canbe stored.

By adopting an amorphous mainspring as a power source for the drivingmechanism of a timepiece or a music box, therefore, it is possible toimprove the energy volume density capable of being stored in themainspring without the need to modify the geometry of the other partssuch as the barrel drum. It is thus possible to achieve a long-timeoperation of the power source for the driving mechanism while permittingdownsizing, and therefore, the amorphous; mainspring is particularlysuitable as a power source for the driving mechanism of a wristwatchrequiring utmost efforts for downsizing.

When a spring comprising the amorphous metal as described above is usedas a hairspring or a mainspring, it should preferably be a mainspringcomprising a non-magnetic material. If the mainspring comprises anon-magnetic material, magnetic resistance is improved. Even when themainspring is attracted by a magnetic field, properties of themainspring are never deteriorated. When a spring comprising an amorphousmetal is used for a fixed spring or a click spring for a crystaloscillator, the spring, if comprising a non-magnetic material, permitsimprovement of magnetic resistance, and the wielding force of the springis never affected by a magnetic field or the like, as in theaforementioned case.

2. Optimum Shape of Spring Comprising Amorphous Metal

A spring comprising an amorphous metal should preferably have across-sectional shape of a circle having a diameter of at least 0.05 mm,or a rectangle having a size of at least a thickness of 0.01 mm×a widthof 0.05 mm.

More specifically, when the spring has such a cross-sectional shape, asufficient wielding force is available. It is therefore applicable asfixing means of a crystal oscillator, a hairspring wielding a timedannular balance serving a governor for a mechanical timepiece, or amainspring serving as a power source for a driving mechanism.

A spring comprising an amorphous metal should preferably have asubstrate or a main plate into which it is incorporated with an initialflexure.

Presence of an initial flexure prevents a play or a shift of the springfrom occurring even incorporated in a substrate or a main plate. Whenthere is an initial flexure, it is possible to apply a load frombeginning. In a spring of the conventional material, a high Young'smodulus results in a reduced allowance to the allowable stress. In thespring comprising the amorphous metal, in contrast, having a low Young'smodulus, a sufficient margin of the allowable stress is ensured evenwhen the initial flexure applies a load.

Further, when the aforementioned spring comprising the amorphous metalis used as a mainspring serving as a power source for a drivingmechanism, this mainspring has a free-exploded shape of an S, and thecurvature changing point where the curving direction of thefree-exploded shape changes should preferably be located on the innerend side from the middle point between an inner end on the winding sideand the other end which is an outer end.

The free-exploded shape of a mainspring means an exploded shapeavailable when releasing the mainspring from the constraint, such as theshape of the mainspring taken out from the barrel drum.

In the free-exploded shape of the mainspring comprising a conventionalmaterial, as in graph G shown in FIG. 3, the shape is formed into an Sclosest to an ideal curve in which the curvature changing point (wherethe radius of curvature p is infinite, and the curving direction of themainspring changes) is provided at the middle point C between the innerend and the outer end of the mainspring. The reason is as follows:

1. To previously reforming the mainspring in a direction counter to thewinding direction to store as much as possible energy in the mainspringupon tightening the mainspring; and

2. To prevent breakage of the mainspring caused by stress concentrationby causing the bending stress to uniformly act on the entire mainspring.

On the other hand, as described above, the amorphous mainspring has asmaller Young's modulus than in the conventional mainspring material,and this alleviates the limitation imposed by the second reasonmentioned above, permitting reforming solely to achieve what isdescribed in paragraph number 1 above.

More specifically, an optimum free-exploded shape of the amorphousmainspring is determined as follows.

If the spiral shape of a mainspring housed in a barrel drum upon tightlywinding is assumed to be an Archimedes' spiral, and polar coordinates rand 0 and adopted, r is expressed as:r=(t/2π)·θ  (16)(where, t: mainspring thickness)

The conditions giving an ideal curve permitting available stressconcentration over the entire mainspring is obtained from the followingequation when assuming that the bending moment acting on the mainspringis M, bending rigidity of the mainspring is B, the radius of curvatureof the mainspring in the free-exploded shape is ρ0, and the radius ofcurvature of the outer periphery portion of the mainspring upontightening is ρ1:(1/ρ1)−(1/ρ0)=M/B=constant  (17)The conditions for achieving the maximum elastic energy as stored in themainspring as a whole are provided by the following equation on theassumption that the maximum amount of elastic strain of the mainspringis εmax:B/M=t/4εmax  (18)

When the mainspring length as measured along the curve from the windingstart center is L′, the following relationship stands:1/ρ1=(π/tL′)^(1/2)  (19)

Therefore, from equations (17) and (19):1/ρ0=(π/tL′)^(1/2) −M/B  (20)

Because the inner end of the mainspring is actually wound on the barrelarbor, the actual mainspring length L is as follows on the assumption ofa barrel arbor radius γ:L=L′−πr ² /t  (21)The metal equation for the ideal curve shape is as expressed by equation(22):ρ0=2(π/t)×(B/M)³×(1/L)+B/M  (22)

Therefore, the radius of curvature σ0 in the free-exploded shape at themaximum energy stored in the mainspring can be expressed, from equations(18) and (22), as follows:ρ0=2(π/t)×(t/4εmax)³×(1/L)+t/4εmax  (23)

With εmax=0.02, the pitch of the spiral shape of the ideal curve becomescompletely smaller than the thickness t of the mainspring. Actually,therefore, a shape close to εmax=0.02 would be used in place of theresult of calculation.

Representation of equation (23) in FIG. 3 described above would take theform of graph G4: it suggests the possibility of forming a calculatedcurvature changing point on the inner side from graph G3 of a mainspringmade of the conventional material.

With the amorphous mainspring, it is therefore possible to reform theentire length of the mainspring in a direction counter to the windingdirection, and thus to increase the stored energy upon tightly winding.

The foregoing equation (1) is a basic equation for theoreticalcalculation, and equation (22) is as well a theoretical equationdeterminable from this basic equation. In practice, it is necessary totake account of occurrence of frictions between mainsprings and betweenthe mainspring and the barrel drum and the necessity of a winding marginfor connecting the mainspring and the barrel arbor.

Therefore, when the correction coefficient of frictions is K1, and thenumber of turns for winding the mainspring around the barrel arbor, therelationship between the number of turns N and the output torque T forthe mainspring of the conventional material is:T=K1−(Ebt ³π/6L)×(N−No)  (24)

Therefore, as shown in FIG. 4, as compared with the output torqueproperty G6 of the mainspring of the conventional material, the outputtorque property G5 of the amorphous mainspring exhibits, though with thesame number of turns, a smaller inclination of the curve and a smallerchange in torque caused by a change in the number of turns. Because thesame number of torque leads to a higher torque, the period of enduranceincreases, and the driving mechanism can be operated for a longer periodof time.

3. Formation of Amorphous Mainspring in Optimum Shape

When using the above-mentioned spring made of the amorphous metal as amainspring, an amorphous mainspring should preferably be manufactured byintegrally laminating two, three or more amorphous metal sheets, sinceit is difficult to manufacture a mainspring having a thickness t of over50 μm from a single sheet.

More specifically, because amorphous metal sheets are laminated, as isknown from equations (1), (22) and (23), it is possible to freely set anamorphous mainspring thickness t in response to the required performanceincluding an output torque.

When integrally laminating the sheets, the plurality of amorphous metalsheets should preferably be bonded with a synthetic resin adhesive.

The synthetic resin adhesive permits achievement of integral laminationof the plurality of amorphous metal sheets at a relatively lowtemperature. Properties of the amorphous metal therefore never change,and the aforementioned features of the amorphous mainsprings are neveraffected.

More particularly, it suffices to adopt an adhesive which sets at atemperature of up to about 300° C., i.e., the temperature at whichproperties of the amorphous metal change. An epoxy-based adhesive, forexample, sets at about 100° C., and properties of the amorphous metalnever change at this temperature.

Because the adhesive easily deforms before completion of setting,reforming of the foregoing amorphous mainspring can be easilyaccomplished by winding the same on a jig or the like.

Further, it is not necessary to apply a separate heat treatment forreforming as in the conventional mainspring, thus enabling a simplifiedmanufacturing process of the mainspring. Reforming of the amorphousmainspring can be accomplished also by spot-welding the inner endportion, the curvature changing point portion and the outer end portionof each of the plurality of amorphous metal sheets. Effects similar tothose mentioned above are available also by using the thus integrallylaminated spring as a fixing spring or a click spring of a crystaloscillator.

4. Driving Mechanism Using Amorphous Mainspring

The driving mechanism using the mainspring of the present invention isbased on a mainspring comprising the above-mentioned amorphousmainspring and a train wheel for transmitting mechanical energy of thismainspring. It has a plurality of amorphous mainsprings and a pluralityof barrel drums for housing these mainsprings, wherein the plurality ofbarrel drums simultaneously engage with the train wheel.

More specifically, because the plurality of barrel drums housing theamorphous mainsprings are simultaneously engaged with the train wheel,an output torque composed of superposed torque outputs from theplurality of barrel drums acts on the train wheel, thus making itpossible to cause a large torque to act on the train wheel, and hence tooperate the driving mechanism with a high torque.

In the configuration as described above, phases of engagement of theplurality of barrel drums with the train wheel should preferably shiftfrom each other.

Because the phases of engagement are staggered, a change in torqueproduced by engagement between a barrel drum with the train wheel can beoffset by engagement with another barrel drum. It is thus possible toinhibit dispersion of torque transmitted from the entire barrel drums tothe train wheel and to operate the driving mechanism smoothly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph illustrating the relationship between strain andwielding force for describing operations of the present invention;

FIG. 2 is a schematic view for explaining operations of the presentinvention;

FIG. 3 is a graph illustrating the position of the curvature changingpoint as derived from the relationship between the mainspring length andthe radius of curvature;

FIG. 4 is a graph illustrating the relationship between the number ofturns and the output torque;

FIG. 5 is a plan view illustrating a driving mechanism using anamorphous mainspring of a first embodiment of the invention;

FIG. 6 is a sectional view of the driving mechanism of the firstembodiment shown in FIG. 5 taken along line A—A;

FIG. 7 is another sectional view of the driving mechanism of the firstembodiment shown in FIG. 5 taken along line B—B;

FIGS. 8A-B are plan views illustrating a mainspring housed in a barreldrum in the first embodiment shown in FIG. 5;

FIG. 9 is a sectional view of the mainspring of the embodiment shown inFIG. 5 cut along the thickness direction thereof;

FIG. 10 is a plan view illustrating a free-exploded shape of themainspring in the embodiment shown in FIG. 5;

FIG. 11 is a partially cutaway plan view illustrating a drivingmechanism of a second embodiment of the invention;

FIG. 12 is a partially cutaway plan view illustrating engagement betweenbarrel drums and a train wheel in the second embodiment shown in FIG.11;

FIG. 13 is a plan view illustrating the structure of a timed hairspringof a third embodiment of the invention;

FIG. 14 is a sectional view illustrating the structure of the timedhairspring of the third embodiment in the third embodiment shown in FIG.13 taken along line C—C; and

FIG. 15 is a side view illustrating a fixing structure of a crystaloscillator of a fourth embodiment of the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will now be described withreference to the drawings.

A first embodiment relates to a driving mechanism using the spring ofthe invention as a mainspring. FIG. 5 is a plan view illustrating adriving mechanism of a electronically controlled mechanical timepieceusing the amorphous mainspring of the first embodiment of the invention;and FIGS. 6 and 7 are sectional views thereof.

The driving mechanism 1 of the electronically controlled mechanicaltimepiece is provided with a barrel drum 30 having an amorphousmainspring 31, a barrel gear 32, a barrel arbor 33 and a barrel cover34. The amorphous mainspring 31 has an outer end connected to the barrelgear 32 and an inner end fixed to the barrel arbor 33. The barrel arbor33 is supported by a main plate 2 and a train wheel bridge 3, andsecured by a ratchet wheel screw 5 to as to rotate integrally with aratchet wheel 4.

The ratchet wheel 4 engages with a click 6 so as to rotate clockwise butnot counterclockwise. Because the method of winding the amorphousmainspring 31 by rotating the ratchet wheel 4 clockwise is the same asin automatic winding or manual winding of a mechanical timepiece,description thereof is omitted here.

Rotation of the barrel gear 32 is increased to seven times as high andtransmitted to a center wheel 7, then sequentially, 6.4 times to a thirdwheel 8, 9.375 times to a second wheel 9, three times to a fifth wheel10, ten times to a sixth wheel 11, and ten times to a rotor 12: therotation speed is thus increased to 126,000 times as high, and thesewheel gears compose a train wheel.

A cannon pinion 7 a is secured to the center wheel 7, a minute hand 13,to the cannon pinion 7 a, and a second hand 14, to the second wheel 9.In order to rotate the center wheel at 1 rph, and the second wheel 9 at1 rpm, therefore, it suffices to perform control so as to rotate therotor 12 at 5 rps. At this point, the barrel gear 1 b rotates at{fraction (1/7)} rph.

As depicted in FIG. 6, the amorphous mainspring 31 is spiral in shapeand is arranged to lie in a single plane.

This electronically controlled mechanical timepiece has a generator 20comprising a rotor 12, a stator 15, and a coil block 16. The rotor 12comprises a rotor magnet 12 a, a rotor pinion 12 b and a rotor inertiadisk 12 c. The rotor inertia disk is for minimizing dispersion ofrevolutions of the rotor 12 against dispersion of driving torque fromthe barrel drum 30. The stator 15 is formed by winding 40,000 turns ofstator coil 15 b onto a stator body 15 a.

The coil block 16 is made by winding 110,000 turns of coil 16 b onto amagnetic core 16 a. The stator 15 a and the magnetic core 15 b are madeof PC permalloy or the like. The stator coil 15 b and the coil 16 areconnected in series so as to give an output voltage added withrespective generated voltage.

AC output generated by the generator 20 as described above is fed to acontrol circuit incorporated with a view to controlling speed adjustmentand to turn-on/off of the driving mechanism 1, although not shown inFIGS. 5 to 7.

Then, the internal structure of the aforementioned barrel drum 30 willbe described with reference to FIG. 8.

FIG. 8(A) illustrates a state in which the aforesaid amorphousmainspring 31 is tightly wound in the barrel drum 30; and FIG. 8(B)shows a state after the amorphous mainspring 31 is released in thebarrel drum.

The amorphous mainspring 31 has a size comprising a width b of 1 mm, athickness t of 0.1 mm, and a total length L of 300 mm.

As described above, the amorphous mainspring 31 has the inner end 311wound onto the barrel arbor 33, and the outer end 312 connected andfixed to the inner surface of the barrel arbor.

When the barrel drum 30 is rotated by an external force relative to thebarrel arbor 33 in the state of FIG. 8(B), the amorphous mainspring 31is tightly wound. When, after tight winding, the mainspring is releasedfrom constraint of the barrel drum 30, the barrel drum 30 rotates alongwith rewinding of the amorphous spring 31. The train wheel including thecenter wheel 7 described above is rotated by the barrel gear 32 formedon the outer periphery of the barrel drum 30, leading to operation ofthe minute hand 13 and the second hand 14.

The amorphous mainspring 31 is formed by integrally laminating aplurality of amorphous metal sheets 313 each having a thickness of 50 μmas shown in FIG. 9, and the individual amorphous metal sheets 313 arebonded with each other with an epoxy-based adhesive 314.

The amorphous mainspring 31 removed from the barrel drum 30 is reformedin a direction counter to the winding direction onto the barrel arbor33, and has substantially an S-shaped free-exploded shape in a planview.

The curvature changing point 315 where the curving direction changes isformed near the inner end 311. The portion between the curvaturechanging point 315 and an inner end 311 is used for securing theamorphous mainspring 31 to the barrel arbor 33.

When manufacturing such an amorphous mainspring 31, the amorphous metalsheet 313 is first fabricated into a width and a length necessary as apower source for the driving mechanism 1.

The individual amorphous metal sheets 313 are bonded to each other withthe use of an epoxy-based adhesive 314 to ensure a thickness t (0.1 mm)necessary for the amorphous mainspring 31.

Finally, before setting of the epoxy-based adhesive 314, the amorphousmainspring 31 is reformed by winding it onto a round rod or the like,and the epoxy-based adhesive 314 is caused to set.

According to the amorphous mainspring 31 of the first embodiment asdescribed above, the following advantages are available.

First, since the amorphous mainspring 31 is adopted as the power sourcefor the driving mechanism 1, it is possible to operate the drivingmechanism 1 for a long period of time while maintaining downsizing ofthe driving mechanism 1.

When a conventional mainspring is incorporated in the aforementioneddriving mechanism 1, operation stops in 40 hours from the tight winding.When the amorphous mainspring 31 is incorporated, in contrast, operationis discontinued in 45 hours from the tight winding, resulting in anincrease in operable hours by about 10%.

Second, because the curvature changing point 315 can be set at aposition near the inner end 311, reforming can be applied oversubstantially the entire length of the amorphous mainspring 31, thusmaking it possible to increase mechanical energy stored by the amorphousmainspring 31, and further extend operating hours of the drivingmechanism 1.

The amorphous mainspring 31 has only a slight dispersion of torque. Whenadopting it as a power source of a mechanical timepiece, therefore, itis possible to improve driving accuracy.

Third, in the conventional art, a mainspring having a prescribedthickness has been obtained by repeatedly rolling a bulk material.

The above-mentioned amorphous mainspring 31 can easily be manufacturedinto a wire, a ribbon or the like by the single-roll process, thedual-roll process or the rotation underwater spinning process. It istherefore possible to simplify the manufacturing process of theamorphous mainspring.

Finally, a plurality of amorphous metal sheets 313 are integrallylaminated with the use of an epoxy-based adhesive 314. A heating processis not therefore necessary for forming the amorphous mainspring 31, andproperties of the amorphous metal are never damaged.

Since reforming can be effected before setting of the adhesive,reforming can be accomplished easily by, for example, winding themainspring 31 onto a jig or the like.

A driving mechanism using the amorphous mainspring of a secondembodiment of the invention will now be described. For the same orsimilar components as those already explained, description will beomitted or simplified hereafter.

In the driving mechanism 1 of the aforementioned first embodiment, onlyone amorphous mainspring 31 housed in the barrel drum 30 has served asthe power source for operating the driving mechanism 1.

The driving mechanism 101 of the second embodiment differs from that ofthe first embodiment, as shown in FIG. 11, in that the driving mechanism101 has two barrel drums, and amorphous mainsprings 31 housed thereinserve as power sources for the driving mechanism 101.

Barrel gears 32 (not shown in FIG. 11) formed on the outer peripheriesof two barrel drums 30 simultaneously engage with a base gear 71 of acenter wheel 7 of the driving mechanism 101.

The two barrel drums 30 rotate in the same direction around respectivebarrel arbors 33, and a torque 2T comprising the sum of values of outputtorque T of the individual amorphous mainsprings 31 acts on the centerwheel 7.

For the barrel gears 32 engaging with the center wheel 7, as shown inFIG. 12, engagement phases are different between the barrel gear 32 tothe left and the barrel gear 32 to the right. At the moment when theleft barrel gear 32 comes into contact with the center wheel 7 at pointB1, the right barrel gear is about to leave the center wheel 7 at pointB2.

Such a difference in phase depends upon the relative positions of thebarrel arbors 33. As is known from FIG. 11, the engagement phase can beadjusted in response to the angle 0 between the rotational center of thecenter wheel 7 and the barrel arbor 33.

According to the driving mechanism 101 using the amorphous mainspring ofthe second embodiment as described above, the following advantages areavailable in addition to those described above as to the firstembodiment. Because the two barrel drums 30 housing the amorphousmainsprings 31 are simultaneously engaged with the center wheel 7forming the train wheel, it is possible to cause the center wheel 7 torotate by superposing values of output torque T of the respective barreldrums 30, and thus to operate the driving mechanism 101 at a high outputtorque 2T.

Because the phases of the barrel gears 32 engaging with the center wheel7 are staggered, operation of the driving mechanism 101 can be smoothedby inhibiting changes in the transmitted torque through alleviation oftorque dispersion produced from a state of engagement between, forexample, the left barrel drum 30 and the center wheel 7 in FIG. 12 bymeans of the state of engagement with the other right barrel drum 30.

A third embodiment of the invention will now be described. In the thirdembodiment, the spring made of the amorphous metal of the invention isused as a hairspring for wielding a timed annular balance forming agovernor of a mechanical timepiece. A balance hairspring 400 serving asa governor in this embodiment comprises, among others, a balance arbor410, an annular balance 420, a double roller 430, a collet 440, a stud450, and a regulator 460, as shown in FIGS. 13 and 14.

The annular balance 420, the double roller 430, and the collet 440 aresecured to the balance arbor 410 so as to permit integrated rotation. Ahairspring 470 is a non-magnetic spring made of an amorphous alloy, hasan inner peripheral end fixed to the collet 440, and an outer end fixedto the stud 450. The regulator 460 comprises, among others, a regulatorpin 461 and a regulator key 462, and the outermost peripheral portion ofthe hairspring 470 passes between the regulator pin 461 and theregulator key 462.

As also shown in FIGS. 13 and 14, the hairspring 470 is spiral in shapeand is arranged to lie in a single plane.

In the balance hairspring 400, when the annular balance 420 rotatesaround the balance arbor 410 as the axis, the collet 440 rotates alsoalong with this. The wielding force of the hairspring 470 acts on theannular balance 420. Upon achievement of a balance between this wieldingforce and inertia of the hairspring 470, rotation of the annular balance420 stops, and the wielding force of the hairspring 470 causes theannular balance 420 to rotate in the reverse direction. That is, theannular balance 420 repeats oscillation with the balance arbor 410 asthe axis. The oscillation period of the annular balance 420 can bechanged by finely adjusting the position of the regulator key 462. Thisoscillation period T varies also with the inertia moment J of therotating portion such as the annular balance as well as with materialproperties of the hairspring 471). When the hairspring 470 is assumed tohave a width b, a thickness t, a spring length L, and a Young's modulusE of the hairspring, T is expressed by the following equation (25):$\begin{matrix}{T = {2\pi\quad\sqrt{\frac{12{JL}}{{Ebt}^{3}}}}} & (25)\end{matrix}$

According to the third embodiment of the invention—as described above,the following advantages are available.

Because the hairspring 470 is made of an amorphous metal, changes inYoung's modulus E caused by a change in temperature are slight, withsmall changes in the oscillation period of the balance hairspring 400 asexpressed by equation (25), thus making it possible to improve accuracyof a mechanical timepiece having a governor including the balancehairspring 400.

Since the hairspring 470 is made of a non-magnetic amorphous metal,magnetic resistance is improved, and even when the hairspring 470 isattracted by an external magnetic field or the like, mainspringproperties are never impaired.

A fourth embodiment of the invention will now be described. The fourthembodiment uses a spring made of the amorphous metal of the invention asa spring for fixing a crystal oscillator of a crystal oscillator typetimepiece in a wielded state. More specifically, as shown in FIG. 15,the crystal oscillator 500 comprises, among others, a vacuum capsule501, and a tuning fork type oscillator 502 housed in this vacuum capsule501. An oscillation circuit is formed by a terminal 503 provided at anend of the vacuum capsule 501 and electrically connected to a circuitboard 510.

The crystal oscillator 500 as described above is arranged on a mainplate 520, and fixed thereto while being wielded by a screw 530 and afixing spring 540 made of art amorphous metal in a direction of beingpressed against the main plate 520.

According to the fourth embodiment of the invention, the followingadvantages are available. The fixing spring 530 made of an amorphousmetal has a low Young's modulus. The relationship between the amount offlexure of the fixing spring 530 and the wielding force therefore takesthe form of graph G2 showing a smaller inclination than in graph GI ofthe spring made of the conventional material as shown in FIG. 1. Evenupon occurrence of a change in the amount of flexure of the fixingspring 530, therefore, a change in the wielding force becomes smaller,thus permitting reduction of the shift of period of the crystaloscillator, and hence, improvement of accuracy of the crystal oscillatortype timepiece.

The present invention is not limited to the aforementioned embodiments,but includes also the following variants.

While, in the first embodiment described above, the amorphous mainspring31 has been used as the power source of the driving mechanism I for theelectronically controlled mechanical timepiece, application of theinvention is not limited to this, but the amorphous mainspring may beused for a driving mechanism of an ordinary mechanical timepiece havinga control system comprising a governor and an escapement.

In the first embodiment described above, the amorphous mainspring 31 hasbeen used as the power source for the driving mechanism 1 of atimepiece. Application of the present invention is not however limitedto this, but the amorphous mainspring may be used as a power source fora driving mechanism of a music box or the like.

Further, while the amorphous mainsprings 31 have been integrallylaminated by the use of the adhesive 314, integration may beaccomplished through spot welding of the inner end 311, the outer end312 and the curvature changing point 315. Reforming of the amorphousmainspring can be conducted to some extent in this manner simultaneouslywith integral lamination.

In the second embodiment mentioned above, the two barrel drums 30 havebeen engaged with the center wheel 7 forming the train wheel. More thantwo barrel drums 30 may however be engaged. The number of barrel drums30 may be appropriately selected in response to the energy stored in theamorphous mainspring and the energy required as a power source of thedriving mechanism.

In the fourth embodiment described above, the spring made of anamorphous metal has been used as the fixing spring 530 for fixing thecrystal oscillator 500, but application is not limited to this. Morespecifically, the spring forming the click 6 engaging with the ratchetwheel 4 in the first embodiment may be made of an amorphous metal. Theclick is provided for preventing back-winding when winding themainspring in the barrel drum, and the spring functioning at this pointis the click spring. The click spring is therefore subjected to arepeated load by a number of teeth of engagement with the ratchet wheelin engagement with the click during winding of the mainspring, and thisnumber of times reaches several tens of thousand or even severalhundreds of thousand. When such a repeated load is applied, theallowable stress of the click spring should be set to less than ½ of themaximum stress. By using a spring made of an amorphous metal as such aclick spring, therefore, it is possible to set a high allowable stress,with smaller dispersion of the wielding force, and the click isfavorable also as a click spring.

In addition, the detailed structure and shape for the application of thepresent invention may be other structure or shape within a range inwhich the other objects of the invention is achievable.

INDUSTRIAL APPLICABILITY

The spring, the mainspring, the hairspring and the driving mechanism andthe timepiece using these springs of the invention is suitablyapplicable as a power source of a driving mechanism for a timepiece, amusic box or the like, as a spring for fixing a crystal oscillator in acrystal oscillator type timepiece or the like, as a hairspring forwielding a timed annular balance of a mechanical timepiece, and as aclick spring for preventing back-winding upon winding a mainspring in abarrel drum.

1. A timepiece comprising: a mainspring; and a substrate receiving atleast a portion of the mainspring, wherein said mainspring is formed ofspirally arranged amorphous metal having an S-shaped free exploded shapeso that when the mainspring is mounted on the substrate the mainspringhas an initial flexure, and said mainspring is spirally arranged so asto lie in a plane.
 2. A timepiece as recited in claim 1, wherein saidmainspring includes an inner end which serves as a winding side for saidmainspring, and an outer end, wherein said free-exploded S-shape has acurvature changing point where the curvature of the free-exploded shapechanges, said curvature changing point being located at a point closerto said inner end than to a point midway between said inner end and saidouter end.
 3. A timepiece as recited in claim 1, wherein said mainspringcomprises Ni—Si—B, Ni—Si—Cr, Ni—B—Cr or Co—Fe—Cr amorphous metal.
 4. Atimepiece as recited by claim 1, wherein said mainspring has a σmax(kgf/mm²) of at least 340 and an E (kgf/mm²) in the range of9,000-12,000.
 5. A timepiece as recited by claim 1, wherein saidmainspring has a circular cross-sectional diameter of at least 0.05 mm,or a retangular cross-sectional shape at least 0.01 mm thick and atleast 0.05 mm wide.
 6. A timepiece as recited by claim 1, wherein saidtimepiece is an electronically controlled mechanical timepiece furthercomprising a driving mechanism, a generator and a control circuit,wherein said generator provides an AC output to said control circuit forcontrolling speed adjustment and to turn said driving mechanism on andoff.
 7. A timepiece as recited by claim 1, wherein said mainspringcomprises an amorphous metal, said mainspring is manufactured using anyof a single roll process, a dual roll process or a rotation underwaterspinning process.
 8. A timepiece as recited by claim 1, wherein saidmainspring comprises a non-magnetic amorphous metal.
 9. A timepiece asrecited by claim 1, wherein said mainspring comprises an amorphousmetal, and said mainspring is manufactured by integrally laminating atleast two amorphous metal sheets.
 10. A timepiece comprising: ahairspring; and a substrate receiving at least a portion of thehairspring, wherein said hairspring is formed of spirally arrangedamorphous metal having an S-shaped free exploded shape so that when thehairspring is mounted on the substrate the hairspring has an initialflexure imparted thereto, and said hairspring is spirally arranged so asto lie in a plane.
 11. A timepiece as recited in claim 10, wherein saidhairspring includes an inner end which serves as a winding side for saidhairspring, and an outer end, wherein said free-exploded S-shape has acurvature changing point where the curvature of the free-exploded shapechanges, said curvature changing point being located at a point closerto said inner end than to a point midway between said inner end and saidouter end.
 12. A timepiece as recited by claim 10, wherein saidhairspring comprises Ni—Si—B, Ni—Si—Cr, Ni—B—Cr or Co—Fe—Cr amorphousmetal.
 13. A timepiece as recited by claim 10, wherein said hairspringhas a σmax (kgf/mm²) of at least 340 and an E (kgf/mm²) in the range of9,000-12,000.
 14. A timepiece as recited by claim 10, wherein saidhairspring has a circular cross-sectional diameter of at least 0.05 mm,or a rectangular cross-sectional shape at least 0.01 mm thick and atleast 0.05 mm wide.
 15. A timepiece as recited by claim 10, wherein saidhairspring comprises an amorphous metal, said hairspring is manufacturedusing any of a single roll process, a dual roll process or a rotationunderwater spinning process.
 16. A timepiece as recited by claim 10,wherein said hairspring comprises a non-magnetic amorphous metal.
 17. Atimepiece as recited by claim 10, wherein said hairspring comprises anamorphous metal, and said hairspring is manufactured by integrallylaminating at least two amorphous metal sheets.
 18. A drive mechanismfor a precision machine comprising: two barrel drums; two mainspringsmounted, respectively, in the two barrel drums, each mainspring beingformed of spirally arranged amorphous metal having an S-shaped freeexploded shape so that when the mainspring is mounted in the barrel drumthat mainspring has an initial flexure imparted thereto, and saidmainspring is spirally arranged so as to lie in a plane; and a trainwheel, said barrel drums simultaneously engaging said train wheel, fortransmitting mechanical energy from said two mainsprings.
 19. A drivemechanism as recited in claim 18, wherein said two barrel drums arephase shifted from each other when they engage said train wheel.
 20. Adrive mechanism as recited in claim 18, wherein at least one of saidmainsprings comprises Ni—Si—B, Ni—Si—Cr, Ni—B—Cr or Co—Fe—Cr amorphousmetal.
 21. A drive mechanism as recited by claim 18, wherein at leastone said mainspring has a σmax (kgf/mm²) of at least 340 and an E(kgf/mm²) in the range of 9,000-12,000.
 22. A drive mechanism as recitedby claim 18, wherein at least one said mainspring has a circularcross-sectional diameter of at least 0.05 mm, or a rectangularcross-sectional shape at least 0.01 mm thick and at least 0.05 mm wide.23. A drive mechanism as recited by claim 18, wherein at least one saidmainspring comprises an amorphous metal, and at least one saidmainspring is manufactured using any of a single roll process, a dualroll process or a rotation underwater spinning process.
 24. A drivemechanism as recited by claim 18, wherein at least one said mainspringcomprises a non-magnetic amorphous metal.
 25. A drive mechanism asrecited by claim 18, wherein at least one said mainspring comprises anamorphous metal, and at least one said mainspring is manufactured byintegrally laminating at least two amorphous metal sheets.
 26. A timepiece having a drive mechanism comprising: two barrel drums; twomainsprings mounted, respectively, in the two barrel drums, eachmainspring being formed of spirally arranged amorphous metal having anS-shaped free exploded shape so that when the mainspring is mounted inthe barrel drum that mainspring has an initial flexure imparted thereto,and said mainspring is spirally arranged so as to lie in a plane; and atrain wheel, said barrel drums simultaneously engaging said train wheel,for transmitting mechanical energy from said two mainsprings.
 27. A timepiece as recited in claim 26, wherein said two barrel drums are phaseshifted from each other when they engage said train wheel.
 28. Atimepiece having a drive mechanism as recited by claim 26, wherein atleast one of said mainsprings comprises Ni—Si—B, Ni—Si—Cr, Ni—B—Cr orCo—Fe—Cr amorphous metal.
 29. A timepiece having a drive mechanism asrecited by claim 26, wherein at least one of said mainsprings has a σmax(kgf/mm²) of at least 340 and an E (kgf/mm²) in the range of9,000-12,000.
 30. A timepiece having a drive mechanism as recited byclaim 26, wherein at least on of said mainsprings has a circularcross-sectional diameter of at least 0.05 mm, or a rectanglecross-sectional shape at least 0.01 mm thick and at least 0.05 mm wide.31. A timepiece having a drive mechanism as recited by claim 26, whereinat least one said mainspring comprises an amorphous metal, and at leastone said mainspring is manufactured using at least one of a single rollprocess, a dual roll process or a rotation underwater spinning process.32. A timepiece having a drive mechanism as recited by claim 26, whereinat least one said mainspring comprises a non-magnetic amorphous metal.33. A timepiece having a drive mechanism as recited by claim 26, whereinat least one said mainspring comprises an amorphous metal, and at leastone said mainspring is manufactured by integrally laminating at leasttwo amorphous metal sheets.